dhcpd_compare (code by fridgei, integration by drkitty)

I'd recommend merging this ***after*** #183.

Things tested and verified:

- [x] Two identical files are correctly identified as containing the same data
- [x] Two different files are correctly identified as containing different data
- [x] Two files containing the same data in a different order are correctly identified as containing the same data
- [ ] Specific differences are correctly identified and **concisely** displayed